Selector and automatic tuner for radiocircuits



Jan. 29, 1929. 1,700,282

E. E. BURNS ET AL SELECTOR AND AUTOMATIC TUNER FOR RADIOCIRCUITS Filed April. 12. 1925 INVENTORS if: BUR/vs 7. (or/cw ATTORNEYS PATENT OFFICE.

ELIEB E. BURNS AND THEODORE COHEN, OF CHICAGO, ILLINOIS.

SELECTOR AND AUTOMATIC TUNER FOR BADIOCIRCUITS.

Application filed April 12, 1926. Serial No. 191,547.

Our invention relates to improvementsin selectors and automatic tuners for radio circuits, and it consists in the combinations, constructions, and arrangements herein de- 5 scribed'and claimed. I

An object of our invention is to provide an improvement over that set forth in our rior application, Serial No. 76,814, filed ec. 21, 1925. In said prior application, we Q disclosed an automatic tuning element for tuning a receiving circuit with the incoming wave, this tuning element being controlled by a surge of plate current at resonance. In said application," the circuit ,disclosed in- 1 cluded two stages of radio-frequency, a detector stage, and two stages of audio-freuency. hetuning control element was s own as actuated by a surge of plate current from-the second stage of audio-frequency. 4 L

The present invention is an improvement in that a special tuner tube is used in connection with the second stage of audio-frequency, and the \control circuit is actuated' by a current surge in the plate circuit of the tuner tube. This is of advantage for the following reasons:

It is-imlportant for the best quality of revception, t at is, to receive speech or music without distortion of sound, that the D. .0. components of plate current" should remain practically constant. We accomplish this by the present invention, since in the present form of the device, the D. C. components of the plate current in the receiving circuit may be practically constant, while at the same time, a change of plate current occurs in the plate circuit of the tuner tube. Thus self-tuning is secured without sacrificing the quality of reception. Furthermore, since the grid current of the tuner tube of the present device is practically zero, no energy is absorbed from the receiving circuit.

Our invention is illustrated in the accompanying drawings, forming part of this application, in which Figure 1- is a diagrammatic view of a receivmg circuit, with the automatic tuner and selector connected therew1th,' and Figure 2 'is 1 diagrammatic view of a modified form of control, in which an arm-- plifier is used in connection with the tuner tube. V

'In order that the resent invention may be clearly understoo we describe certain parts of the circuit which have been already described in connection with our said pending application. The two stages of radlo-frequency, the detector stage, and the two stages of audio frequency are electrically connected to each other and to the sources of current in the usual manner.

We'will first describe the selector. We have shown the selector as tuning one of the stages of radio-frequency. It is obvious that theselector may be a separate unit if desired; but, for example, we have connected the selector with the tuning element of one of the radio-frequency circuits. The selector comprises a ratchet 1 which 1s operatively connected to the tuning element 2 in the radio-frequency circuit 3. The teeth 4 in the ratchet 1 may be of any size desired such as, for example, a size sufiicient to turn the tuning element to change the frequency Off the circuit'3 ten kilocycles. It is obvious that any other amount of turning may be substituted for the amount just set forth.

The ratchet 1 is advanced step by step by means of a pawl 5 and the ratchet is held 1n advanced position by means of a second pawl 6. The pawl 5 is actuated bya magnet 7, this magnet being energized by a make-and-break device indicated generally at 8. The make-and-break device, in the present instance, consists of a metal disc having insulating portions 9. A spring pressed terminal 10 yieldingly engages with the periphery of the disc, and when touching the metal between the insulating por-.

tions 9, completes a circuit from a source of current 11 to the magnet 7 This circuit energizes the magnet 7 moving the awl 5, and advancing the ratchet 1 one toot This of course will actuate the tuning element.

The disc 8may be disposed in a room of a hotel, for example, and may hate the call letters of the broadcasting stationsprinted thereon, as at 12. The operator, wishing to tune in the station, merely rotates the disc 8 by means of the knob 13 until the call letters of the desired station are brought into view.

While the disc 8 is being rotated, it will cause the pawl 5 to advance the ratchet 1 and the tuning element2 to the re uired position for the circuit 3 to receivet e signals sent outby the station in question. The ratchet 1, together with vthe .magnet 7 and its associate parts, is disposed adjacent to the tuning element 2 and is electrically connected by the wiressl i 'with the make-anddistant control.

A filament switch 15 is of course provided and may now be turned. on. This switch may also be disposed adjacent to the makeand-break device 8.

We will now describe the automatic tuning-element. This element may be separate from the .radio circuit, if desired, in the same manner as the selector could be a separate unit. However, to simplify the showing, we have made use of another of the radio-frequency stages. The tuning element 16 is operatively connected to a motor 17 by means of a belt 18. This showing is diagrammatic, and it is to be noted that any actuating means for the tuning element 16 may be substituted for the motor 17 without switch- 20.

departing from the spirit and scope of our invention.

The motor is electrically connected with a source of current 19 and with a relay The switch 20 is closed by means of a lever 21, the lever 21 in turn being controlled bya magnet 22. Wires 23 connect the magnet 22 with a source of cur rent 24 and with a control switch 25. Theswitch 25 is disposed adjacent to the ,makeand-break device 8.

The apparatus thus far described is that disclosed in our prior application. The novel feature of the present invention consists in the provision of a tuner tube connected across the secondar 4 1 of the transformer of the last stage 0 amplification, which I haveindicated generally at 28, by -means of wires 42. When a radio receiver is tuned to resonance with received signals, voltage changes take place in the grid and plate circuits which do not occur under other conditions. In the connection shown, the voltage changes act on the grid circuit of the tuner tube, causing variations in the current of the plate circuit. The tuner tube may have difierent grid bias from that of the tube to whose circuit it is connected. Be-

' cause of different grid bias, the average plate current (D. C. component) of the receiver tube may be, practically constant while there is a surge of current in the plate circuit of the tuner tube when the receiver is tuned to resonance withthe received signals. The currentsurge in the plate circuit of the tuner tube is designed to operate the relay instead of the current surges in the receiver circuit proper.

From the foregoing description of the 60 various parts of the device, the operation ing the magnet and actuatingthe lever 21.

thereof may be readily understood. The operat-or, after closing the switch 15 and rotating the dial 8, closes the switch 25; This closes the circuit to the magnet 22,- energiz- The lever 21 in turn closes the motor conwith the radio-frequency circuit 3 and with received signals. At this point, a surge of current from the platecircuit of the tube will flow along the wires 29 and energize the magnet 30. The magnet 30 is wound in such a manner as to actuate the lever 31 when a current of a predetermined value, say one milampere, is produced. The movement of the lever 31 releases the catch 26, thus allowing the spring 32 to open the switch 20. The motor is stopped and therefore ceases to actuate the tuning element 16. The circuits receiving the incoming signal will be held at resonance with each other, and will therefore receive signals from the stations desired. v

In Figure 2, we have shown a'modified form of the device in which the tuner tube has an amplifier 43, and in which the amplified current, due to the surge in the tube 40, is transmitted by the wires 29. to the magnet 30 in the manner described above.

As stated before, two distinct advantages: .are secured over that form of the devicev plate circuit of the tuner tube for operating the magnet 30 to control the motor. Thus self-tuning is secured without sacrificing-the quality of reception. Furthermore, since.

the grid current of the tuner tube is practically zero, no energy is absorbed from the receiving circuit. g

In the drawings, we have shown the tuner tube as beingconnected with the secondary of the last stage of amplification, but it' will be understood that this tuner tube might be connected with the receiving circuit at any point where there are voltage variations, since such voltage variations would cause a corresponding surge of current in the'plate circuit of the tuner tube. The arrangement described above, in which the variations of the current in the plate circuit ofthe tuner tube are made use of to control the tuning element, may be used in any form of receiving circuit, such as the neutrodyne, the superhetrodyne, or the regenerative.

We claim:

1. The combination with a radio circuit, of a tuning element for bringin the circuit into resonance with a receive signal, an electron tube separate from but having its gri d circuit connected to the receiving circuit, and means actuated by a change of the plate current of the tube for controlling the tuning element.

2. The combination with a radio circuit, of a tunlng element for br ngln the circuit mto resonance with a receive slgnal, an

-electron tube separate from but having its grid circuit connected to the receiving circuit, and means actuated by an increase of the platecurrent of the tube for controlling the tuning element.

3. The combination with a radio circuit, of a tuning element for bringing the circuit into resonance with a received signal, .a

"motor for actuating the tuning element, an

electron tube separate from but having its grid circuit connected to the receiving circuit, and means actuated by a change of the plate current of the tube for controlling. the

' motor.

4. The combination with a radio circuit, of a tuning element for bringing the circuit intov resonance with a received signal, a a motor for actuating the tuning element, an electron tube separate from but having its grid circuit connected to the receiving circuit, and a relay actuated by a change of the plate current of the tube for controlling the motor.

5. The combinationwith a radio circuit,

of a tuning element for bringin the circuit 1nto resonance w th a "receive the motor.

signal, an;- electron tube separate from but having its grid circuit connected to the receiving circuit, and means actuated by an amplified surge of current in the tube for controlling the tuning element.

sociated with said radio receiving circuit,

and means actuated by an increase of the.

plate current of said electron tube fbr controlling the tuning element.

8. The combination with a radio receiving circuit, of a tuning element for bringing the circuit into resonance with a rece ved signal, a motor'for actuating the tuning element, an electron tube not a part of but as-- sociated with the receiving circuit, and a relay actuated by a change of the plate current of said electron tube for controlling ELliIER E. BURNS. THEODORE COHEN. 

